1. Field of the Invention
The present invention is directed to an x-ray diagnostics installation operable in a transillumination mode or an exposure mode.
2. Description of the Prior Art
X-ray diagnostics installations are known in the art having components which can be optionally arranged for transillumination or exposure of an examination subject. Such known systems include an x-ray image intensifier with a following video chain, a sheet film changer, an x-ray source and a table or bed for the examination subject. The sheet film changer is mounted on an undercarriage. Such x-ray diagnostics installation offer the possibility of examining the subject in a transillumination mode and, if needed, to produce a direct exposure of a diagnostically relevant area identified in the transillumination mode.
A commercially available x-ray diagnostics installation of this type is the "Puck" system of Siemens-Elema AB, Sweden, as described in Publication No. WS 4788. In this system the x-ray image intensifier is disposed above the patient table on a ceiling mount, and the x-ray source (x-radiator) is disposed in a base of the table. The table has a longitudinally displaceable bearing plate on which the examination subject rests. By means of the carriage on which it is mounted, the sheet film changer can be positioned directly next to the base of the table so that a region of the examination subject, initially transilluminated with the x-ray source and the x-ray image intensifier, can be subsequently positioned in front of the sheet film changer for producing an exposure, by longitudinal displacement of the bearing plate. A second x-ray source disposed on a ceiling mount above the sheet film changer is required for producing this exposure. Apart from the need for two x-ray sources, a disadvantage of this arrangement is that displacement of the examination subject is required in order to change from the transillumination mode to the exposure mode. This is particularly true in the case of angiographic examinations wherein the examination subject is frequently catheterized, or connected to contrast agent injectors, so that displacement of the examination subject cannot be easily undertaken.
The aforementioned Siemens-Elema publication also describes an x-ray diagnostics apparatus wherein only a single x-ray source is required for transillumination and exposure, wherein the x-ray image intensifier and the sheet film changer are arranged side-by-side in the longitudinal direction of the support table in the base thereof beneath the bearing plate. The x-ray source is attached above the bearing plate, and is displaceable together with the bearing plate in the longitudinal direction thereof. To prepare an exposure of a region of the examination subject, which was initially transilluminated, the x-ray source, proceeding from a position in which it is arranged lying opposite the x-ray image intensifier, is displaced together with the bearing plate and the examination subject lying thereon into a position at which the x-ray source lies opposite the sheet film changer. A disadvantage of this system is that the sheet film changer is a fixed component of this system, and thus cannot be used separately. Another disadvantage is that the examination subject again must be shifted in order to change from the transillumination mode to the exposure mode.
A further x-ray diagnostics installation is described in the aforementioned Siemens-Elema publication, wherein the x-ray image intensifier and the x-ray source are attached at opposite ends of an arc-shaped carrier which is height-adjustable, and which can be swivelled in different directions. The sheet film changer is connected to the x-ray image intensifier to form a unit which is pivotable around an axis such that the x-ray image intensifier or the sheet film changer can optionally interact with the x-ray source. This x-ray diagnostic installation permits a simple change to be undertaken from the transillumination mode to the exposure mode, by suitable pivoting of the unit formed of the x-ray image intensifier and the sheet film changer without dislocating the examination subject. A disadvantage of this system, however, is that the arc is stationarily attached in the longitudinal direction of the support table, so that a longitudinal displacement of the bearing plate with the examination subject lying thereon still is required for certain examinations, for example, in the case of angiographic examinations wherein the course of a contrast agent injected into the examination subject is to be observed or recorded in successive regions of the examination subject following each other along the table. Again, the sheet film changer is a fixed component of the system, and cannot be used independently thereof.